Glossary
Acetylcholine (ACh)
A neurotransmitter involved in muscle action, learning, and memory.
Example:
Low levels of Acetylcholine (ACh) are strongly linked to the memory deficits seen in Alzheimer's disease.
Action Potential
A brief electrical charge that travels down the axon of a neuron, representing the neuron's 'firing' state.
Example:
When you touch a hot stove, a rapid action potential zips up your arm to your brain, signaling pain.
Agonists
Drugs or chemicals that mimic the effects of a neurotransmitter, binding to its receptor and activating it.
Example:
Some pain medications act as agonists for endorphins, producing a feeling of euphoria and reducing pain.
All-or-none response
The principle that a neuron's action potential either fires completely or not at all, with no partial firing.
Example:
Just like flipping a light switch, a neuron's all-or-none response means it either sends a full signal or no signal at all.
Antagonists
Drugs or chemicals that block the effects of a neurotransmitter, preventing it from binding to its receptor.
Example:
A drug used to treat schizophrenia might be an antagonist that blocks dopamine receptors, reducing overactivity.
Axon
A long, slender projection of a neuron that transmits electrical impulses away from the cell body to other neurons, muscles, or glands.
Example:
When you decide to kick a ball, the signal travels down the axon of a motor neuron to reach your leg muscles.
Cell Body (Soma)
The main part of a neuron that contains the nucleus and maintains the cell's life functions.
Example:
The cell body acts like the neuron's control center, processing incoming signals and deciding whether to fire.
Dendrites
Branch-like extensions of a neuron that receive chemical signals from other neurons.
Example:
Imagine a neuron's dendrites as tiny antennas constantly picking up messages from neighboring brain cells.
Depolarization
The process during an action potential when the inside of the neuron becomes more positive due to the influx of positively charged ions.
Example:
During depolarization, the neuron's internal charge flips from negative to positive, initiating the electrical impulse.
Dopamine
A neurotransmitter that influences movement, learning, attention, and emotion.
Example:
The pleasure you feel when eating your favorite food is partly due to the release of dopamine in your brain's reward pathways.
Endorphins
Natural opiate-like neurotransmitters linked to pain control and pleasure.
Example:
The 'runner's high' experienced after intense exercise is often attributed to the release of endorphins.
Excitatory Signals
Neurotransmitter signals that increase the likelihood of a postsynaptic neuron firing an action potential.
Example:
Receiving excitatory signals is like pressing the gas pedal on a car, making the neuron more likely to 'go'.
GABA
A major inhibitory neurotransmitter in the brain, which calms neural activity.
Example:
Medications for anxiety often enhance the effects of GABA, helping to reduce overstimulation in the brain.
Glutamate
A major excitatory neurotransmitter, crucial for learning and memory formation.
Example:
Too much glutamate can overstimulate the brain, potentially leading to migraines or seizures.
Inhibitory Signals
Neurotransmitter signals that decrease the likelihood of a postsynaptic neuron firing an action potential.
Example:
When a neuron receives inhibitory signals, it's like pressing the brakes, making it less likely to fire.
Myelin Sheath
A fatty layer that insulates the axon of some neurons, significantly increasing the speed of neural impulse transmission.
Example:
The myelin sheath allows your brain to process information incredibly fast, like a high-speed internet connection for your nerves.
Neuron
The fundamental building block of the nervous system, responsible for transmitting information through electrical and chemical signals.
Example:
Your ability to read this sentence relies on billions of interconnected neurons firing rapidly in your brain.
Neurotransmitters
Chemical messengers that transmit signals across the synaptic gap between neurons.
Example:
Our moods, thoughts, and actions are all influenced by the complex dance of neurotransmitters in our brains.
Norepinephrine
A neurotransmitter involved in alertness and arousal, as well as mood.
Example:
When you're startled by a loud noise, a surge of norepinephrine helps prepare your body for a 'fight or flight' response.
Refractory Period
A brief period after a neuron has fired an action potential, during which it cannot fire again.
Example:
After sending a signal, a neuron enters a refractory period, like a camera flash recharging before it can take another picture.
Resting Potential
The stable, negative electrical charge of a neuron when it is inactive and not transmitting a signal.
Example:
A neuron maintains its resting potential like a coiled spring, ready to release energy when stimulated.
Reuptake
The process by which excess neurotransmitters in the synaptic gap are reabsorbed by the sending neuron.
Example:
Antidepressants often work by blocking reuptake, allowing more serotonin to remain in the synapse and prolong its effect.
Serotonin
A neurotransmitter that affects mood, hunger, sleep, and arousal.
Example:
Many antidepressant medications work by increasing the availability of serotonin in the brain to improve mood.
Synapse
The tiny gap between the axon terminal of one neuron and the dendrite or cell body of another neuron, where chemical communication occurs.
Example:
Information jumps across the synapse like a tiny bridge, allowing neurons to communicate without physically touching.
Terminal Branches
The branched endings of an axon that contain synaptic vesicles and release neurotransmitters into the synapse.
Example:
At the end of a neural pathway, the terminal branches are where the neuron 'speaks' to the next cell by releasing chemical messengers.
Threshold
The minimum level of stimulation required for a neuron to fire an action potential.
Example:
Unless the incoming signals reach a certain threshold, the neuron will not activate and send a message.